Heretofore there have been a number of different commercial processes and products developed relating to a pressure sensitive adhesive laminate and to the provision of splitless releasable liner or backing sheets positioned on such laminates.
In one patent on a method of making a paper laminate having appreciably compacted score lines in connection with achieving a splitless release liner or backing, Morgan U.S. Pat. No. 3,859,157, the inventor is concerned about the humidity of the atmosphere surrounding the apparatus when the release liner is compacted. The inventor is concerned about controlling the humidity in the environment when the backing paper has been coated with a release material, dried and then the paper is exposed to humid air and the paper is rehumidified and stabilized at about 50% relative humidity in the air prior to compaction. After compaction is made under these controlled conditions, a face sheet having a layer of pressure sensitive adhesive thereon is laminated onto the release coated surface of the backing paper.
However, it heretofore has been found to be very difficult, if not impossible, to use all desirable types of face layers in making the laminate of U.S. Pat. No. 3,859,157. This is because the adhesive is applied to the face sheet and it is difficult to apply adhesive directly to a metallic or plastic face sheet under the normal state of the art. Irregularities, slipping, distortion of the face sheet, etc. are some of the problems encountered in coating metallic or plastic face sheets with adhesive. Hence, the prior art has taught the concept of coating the release paper with adhesive and transferring this to the face sheet during lamination, but this is not taught or suggested in U.S. Pat. No. 3,859,157.